textproduct: Albany

SYNOPSIS

Lake effect snow will move into the western Adirondacks early tonight and slowly shift southward into the Mohawk Valley, Capital Region and northern Catskills Friday morning. Heavy snow accumulations will occur where the bands set up mainly west of the Capital Region with some higher total over the northern Taconics and northern Berkshires. High pressure builds in Saturday with cold and dry weather before a pair of systems impact the region Sunday into Monday morning, and also Tuesday with rain and snow, though the Tuesday system could bring a widespread accumulating snow.

SHORT TERM /THROUGH SUNDAY/

Key Messages:

- A period of lake effect snow is expected tonight into Friday across the western Adirondacks, Mohawk Valley and northern Catskills. Snowfall amounts of 4 to 12 inches are expected in the most persistent lake effect bands.

- A Lake Effect Snow Warning remains in effect for Herkimer and Hamilton Counties with Winter Weather Advisories for Fulton, Montgomery, Schoharie, Counties.

- A Winter Weather Advisory for northern Berkshire and eastern Rensselaer Counties for lake effect and upslope enhancement 10 am Fri to 10 pm Sat for 2-5". - Wind gusts between 30 and 45 mph, especially on Friday, could lead to patchy to areas of blowing and drifting snow.

Discussion: As of 230 PM EST...

Happy Thanksgiving!

A positively tilted mid and upper level trough continues to be situated over the eastern CONUS with an H500 closed circulation over southeast Ontario and southwest Quebec this afternoon. In the low to mid-level southwest flow, most of the lake effect activity has been confined to the St Lawrence River Valley and west of the forecast area with occasional snow showers drifting into the western Adirondack. Mostly cloudy, mainly dry and cold conditions have persisted across most of eastern NY and western New England thus far. Any snow accumulations prior to nightfall will be an inch to two well north of Route 28 and Old Forge.

A sfc trough and a mid and upper level short-wave will move across the region tonight. This will allow the Lake Ontario snowband to begin to settle southward over the western Dacks. Snowfall rates could reach an inch or even two an hour due to a multi-lake connection off Lake Superior and Georgian Bay. Lake induced instability on upstream soundings is conditional with the inversion height above 8 kft AGL. The band should begin to move southward between 2-5 am, and may be just north of I-90 in the Mohawk Valley by 7 am and could impact the I-90 corridor 7-10 am based on the 3-km NAM and HRRR. The NAM is a little slower than than the NAM, but the headlines look good and remain up for the western Dacks and western Mohawk Valley (including southern Herkimer Co) with warnings for 4-12". The central Mohawk Valley including Fulton and Montgomery Counties may get 2-6" of snow, as well as Schoharie County in the northern Catskills may get 3-6". The band pushes southward in the afternoon into the Capital Region, northern Taconics and Berkshires. Some 1-2" amounts in the Capital Region are possible. However, due to upslope enhancement with the lake band 2-5" are possible in the Rensselaer Plateau of eastern Rensselaer and the northern Berkshires. The Winter Wx Advisory criteria is only 3" and due to the holiday weekend, an advisory makes sense for these 2 area. The Capital Region will be monitored if higher totals area realized, but special weather statements may be used to track the band tomorrow into tomorrow evening. The lake effect band may intensify again in the pm with less directional shear below 700 hPa, and persistent conditional lake instability. The band exact placement is in question on how far south of the Tri Cities it will be in the mid pm though it may migrate slightly further north in the pm to early evening.

Blowing and drifting snow is expected with a tight sfc pressure gradient in the wake of the sfc trough and some momentum transfer. Gusts will be mainly 25-40 mph, though a few higher ones can not be ruled out. Use caution if out on the roads tomorrow if encountering any lake bands or heavy snow showers. Lows will be in the 20s to around 30F. Black Friday will be blustery and cold with highs in the mid 30s to around 40, except mid 20s to lower 30s over the mtns.

The lake effect band begin to lose its extension in the early evening with the inversion height starting to lower and the multi- lake connection lost. Also, the flow begins to shift anticyclonic. Some light snow amounts may continue in the Hudson River Valley including the Capital Region, as well as the northern Catskills/Taconics and Berkshires. Some locations in the western New England favored upslope areas are forecasted to receive 2-5" again. The lake effect snow showers taper to scattered flurries by Saturday morning. The winds will begin to slightly subside with lows in the 20s with some teens over the Adirondacks Park.

High pressure builds in Saturday with the winds continuing to decrease with partly to mostly sunny and cold conditions. Highs will run about 5-10 degrees below normal with mid 30s to around 40F in the valleys and 20s to lower 30s over the terrain again.

Saturday night into Sunday...high pressure shifts east of the Mid Atlantic and southern New England corridor with mid level ridging weakening over the Northeast, as low pressure approaches from the Midwest and lower Great Lakes Region. Clouds rapidly increase with light snow or snow showers moving into the region late Sat night. Lows fall back into the teens and 20s. The isentropic lift increases across the region on Sunday, as the cyclone moves towards southeast Ontario and Georgian Bay. A period of snow to rain will occur in the lower elevations with the south to southwest flow maintaining snow over the southwest Dacks. We may need an advisory for 2-6" of snow or so over northern Herkimer and Hamilton Counties later. It will become breezy with highs still below normal in the 30s to lower 40s. Snow accums in most locations outside the will be a coating to an inch before the transition to rain outside the Adirondack Park and southern Greens.

LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/

Key Messages:

- The 13Z NBM 24-hr probabilities >4" of snowfall ending 7 am Wed across eastern NY and western New England are 25-40% for the potential storm system Tue-Wed.

Discussion...

The cold front to the weekend system moves through Sunday night with a brief lake effect connection into Monday for light snow accums over the western Dacks, western Mohawk Valley and northern Catskills. Lows fall back into the 20s with some teens over the southern Greens and southern Dacks. Monday will be chilly with high pressure briefly building in before clouds start to increase from the south and west late in the day. Highs will still run about 5-10 degrees below normal with mid 30s to around 40F in the major valleys and 20s to lower 30s over the hills and mtns.

The frontal boundary stalls near the mid Atlantic Seaboard and the Southeast Monday night. Low pressure organizes over the Southeast, as separate northern stream disturbance will be digging in from the Missouri and Midwest corridor. Some over running light snowfall may begin to move into the forecast area late Monday night with a better thrust of snow for Tue. The latest ensembles/NBM/medium range guidance continues to show a storm impacting the forecast area Tue-Wed morning. The track of the system shows spread in the ensembles and the "fuzzy" clustering, though the latest NBM guidance yields 25-40% probs for >4" of snow for the forecast area Tue-Tue night. The evolution and track will make a big difference for a light accumulating snowfall into the Capital Region vs. a heavier one. We have likely PoPs for accumulating snowfall Mon night-Tue night across the forecast area with temps running colder than normal with lows in the teens and 20s and highs in the 20s to lows to mid 30s. The predominant ptype will be snow. Trends on this storm will be monitored over the next few days.

Midweek onward...the storm system pulls away Wed with some lingering light snow and snow showers with high pressure building in. A strong cold front approaches from southeast Canada, the Great Lakes Region and Midwest for Thu with a chance of snow showers and flurries from the Capital Region north and west. Temps will continue to run below normal for early December.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Through 18z Friday...VFR conditions prevail across all TAF sites this afternoon despite clouds largely remaining in place in the wake of a potent cold front. Lake effect snow has already begun as a result, but generally terminals should not be impacted until tomorrow morning when the bands shift southward. Latest satellite imagery indicates some pockets of clearing that will eventually expand to break up ceilings for brief times late this evening. However, with moisture continually streaming into the region off the Lakes, breaks in ceilings will not be long lasting.

VFR conditions should remain consistent, however, through much of the 18z TAF period outside of any snow showers that drift into terminal boundaries and force MVFR to IFR conditions. KGFL looks to be the first to be potentially impacted tonight, but confidence is not high on whether the band will reach far enough eastward into the terminal. Therefore, a PROB30 group was added for those aforementioned MVFR conditions. Greater, though still only low to moderate, confidence exists in KGFL/KALB/KPSF seeing snow showers tomorrow morning into early tomorrow afternoon as the primary lake effect band and surrounding showers drift southward. Here, IFR conditions are more likely, especially for KPSF where upslope flow will enhance snowfall. Additional details will be provided as confidence increases with future iterations. Winds throughout the period will be breezy out of the southwest with sustained speeds ranging from about 10 to 15 kt with gusts of 20 to 25 kt.

Outlook...

Friday Night: Low Operational Impact. Breezy. Slight Chance of SHSN. Saturday: Low Operational Impact. Breezy. NO SIG WX. Saturday Night: Low Operational Impact. Slight Chance of SHSN. Sunday: High Operational Impact. Definite SHRA...SHSN. Sunday Night: Moderate Operational Impact. Chance of SHRA. Monday: No Operational Impact. NO SIG WX. Monday Night: Low Operational Impact. Slight Chance of SN. Tuesday: High Operational Impact. Likely SN.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...Winter Weather Advisory from 10 AM to 10 PM EST Friday for NYZ054. Lake Effect Snow Warning until 1 AM EST Saturday for NYZ032- 033. Lake Effect Snow Warning from 1 AM Friday to 7 AM EST Saturday for NYZ038. Winter Weather Advisory from 1 AM Friday to 7 AM EST Saturday for NYZ039-040-047-082. MA...Winter Weather Advisory from 10 AM to 10 PM EST Friday for MAZ001. VT...None.